Photosynthesis Overview

Question 1

Photosynthetic organisms

Answer 1

Plants
Algae
Portist
Cyanobacteria (blue green algae)

All contains the pigment chlorophyll

Question 2

Chlorophyll

Answer 2

Absorbs light
Made of
Hydrocarbon tail
-anchors molecule into granum

Porphyrin portion

• Mg atom surrounded by hydrocarbon ring with double and single bonds
• electrons absorb light energy
• chlorophyll (a) has a methyl (CH3) at top of ring, chlorophyll b has an aldehyde (-COH) group which determine type of light they absorb

Question 3

Types of chlorophyll

Answer 3

Chlorophyll A (blue green pigment)

Chlorophyll B (yellow green pigment)

Both composed of porphyrin ring attached to hydrocarbon tail

Question 4

Overall equation

Answer 4

6CO2 + 6H2O —-> (sunlight) 6O2 + C6H12O6

Question 5

Cyanobacteria

Answer 5

• Blue green algae
• Unicellular, grown in colonies in water, rocks and soil
• blooms may be toxic to heterotrophs
• no membrane bound organelles, but cell membrane folded carry out PS and CR

Question 6

Cyanobacteria (endosymbiotic theory)

Answer 6

Most likely first ever photosynthetic organisms

Theory- they resemble chloroplasts and may have been engulfed by larger eukaryotic cells

Question 7

Stomata

Answer 7

• Opening on surface of leaf that allows for gas exchange
• generally open during day and closed at night
• controlled by guard cells (guard cells swell -> open stomata, guard cells shrink-> stomata close)

Question 8

Stomata part 2

Answer 8

• Water moves in or out of guard cell by osmosis
• water follows K+ and Cl- which diffuse through guard cell membrane
• when swollen, cells buckle outwards and increase size of stomata
• when limp, cells come close together and stomata shrinks
• blue light in the morning activates receptors in guard cell membranes, and K+ ions move into cells
• water follows, stomata open, photosynthesis occurs in mesophyll